The present invention relates to a method of and device for tightening threaded connectors by tightening tools.
It is known to tighten and loosen threaded connectors, for example bolts by respective bolting tools. The main object of tightening down bolts by bolting tools is to elongate a bolt when turning a nut on a flange to be assembled. The elongation of the bolt provides for a clamping force which holds the flange together. There are several approaches to provide the clamping force. One approach is to use hydraulic torque tools, another approach is to use tensioning tools that elongate the bolts hydraulically, and a further approach is to use turn-of-the nut method. The most common method is to elongate a bolt with the use of controlled torque. Due to the influence of friction between the threads and the surface of the nut and bolt, this method gives pure clamp load accuracy but not bolt elongation. As for tensioning tools which pull and thus elongate the bolts, here the bolt elongation is achieved but it remains inaccurate due to the tendency of the bolt to relax when the tensioner is taken off. The turn-of-the nut method would be ideal if the right staring point from where the bolt elongates could be established accurately. The term "turn-of-the nut" is used here to identify a method in accordance with which a nut is turned on the bolt to clamp the flange together
In the known methods of tightening the threaded connectors based on the turn-of-the nut principle, it has not been possible to provide an exactly desired elongation of the bolt to achieve an exactly desired clamping force. Thus, while this method possesses significant advantages, it could not be implemented efficiently due to the above specified reasons.